Expandable intervertebral implant

ABSTRACT

An implant for therapeutically separating bones of a joint has two endplates each having an opening through the endplate, and at least one ramped surface on a side opposite a bone engaging side. A frame is slideably connected to the endplates to enable the endplates to move relative to each other at an angle with respect to the longitudinal axis of the implant, in sliding connection with the frame. An actuator screw is rotatably connected to the frame. A carriage forms an open area aligned with the openings in the endplates. The openings in the endplates pass through the carriage to form an unimpeded passage from bone to bone of the joint. The carriage has ramps which mate with the ramped surfaces of the endplates, wherein when the carriage is moved by rotation of the actuator screw, the endplates move closer or farther apart.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation patent application Ser. No.13/836,687 filed on Mar. 15, 2013, which is incorporated in its entiretyherein.

FIELD OF THE INVENTION

This invention relates to stabilizing adjacent vertebrae of the spine byinserting an intervertebral implant, and more particularly anintervertebral implant that is adjustable in height.

BACKGROUND OF THE INVENTION

Bones and bony structures are susceptible to a variety of weaknessesthat can affect their ability to provide support and structure.Weaknesses in bony structures have numerous potential causes, includingdegenerative diseases, tumors, fractures, and dislocations. Advances inmedicine and engineering have provided doctors with a plurality ofdevices and techniques for alleviating or curing these weaknesses.

In some cases, the spinal column requires additional support in order toaddress such weaknesses. One technique for providing support is toinsert a spacer between adjacent vertebrae.

SUMMARY OF THE INVENTION

In accordance with the disclosure, an implant for therapeuticallyseparating bones of a joint, the implant defining a longitudinal axisextending between distal and proximal ends, the implant comprises afirst endplate configured to engage a first bone of the joint, andhaving an opening through the endplate, and at least one ramped surfaceon a side opposite a bone engaging side; a second endplate configured toengage a second bone of the joint, and having an opening through theendplate, and at least one ramped surface on a side opposite a boneengaging side; a frame slideably connected to the first and secondendplates to enable the first and second endplates to move relative toeach other at an angle with respect to the longitudinal axis, in slidingconnection with the frame; an actuator screw rotatably connected to theframe; and a carriage (a) forming an open area aligned with the openingsin the first and second endplates and defining thereby a proximalcarriage side and a distal carriage side with respect to thelongitudinal axis, (b) threadably connected to the actuator screw,whereby rotation of the actuator screw moves the carriage with respectto the frame and the first and second endplates, the actuator screw notcrossing between the proximal carriage side and the distal carriageside; and (c) including a plurality of ramps each mateable with at leastone of the at least one ramped surfaces of the first and secondendplates, wherein when the carriage is moved by rotation of theactuator screw, at least one of the at least one ramped surface of thefirst endplate and at least one of the at least one ramped surface ofthe second endplate each slide along at least one of the plurality oframps of the carriage to cause the endplates to move relative to eachother in sliding connection with the frame.

In various embodiments thereof, the first and second endplates areconfined by the frame to move relative to each other only along an axissubstantially transverse to the longitudinal axis; at least one of thefirst and second endplates includes at least one aperture through whicha fastener may pass to secure the implant to bone of the joint; theimplant further includes a blocking mechanism configured to preventbacking out of a fastener passed through at least one of the first andsecond endplates and into body tissue; the blocking mechanism includes ablocking member slideably retained within a channel between anunblocking position and a blocking position in which a portion of theblocking member overlaps a portion of the faster; at least one of thefirst and second endplates includes one or more projections configuredto engage bone of the joint when the implant is positioned between bonesof the joint; at least one of the first and second endplates is composedof two interconnected portions of dissimilar materials; one of thedissimilar materials is metallic and includes at least one aperturethrough which a fastener may be passed to attach the implant to a boneof the joint; one dissimilar material is polymeric, and anotherdissimilar material is metallic; and, the implant further includes apolymeric material configured to press against the actuator screw toreduce a potential for unintended rotation of the actuator screw.

In further embodiments thereof, when the actuator screw is rotated in afirst direction, a height of the implant transverse to the longitudinalaxis is increased, and when the actuator screw is rotated in a seconddirection, a height of the implant transverse to the longitudinal axisis decreased; the actuator screw is threadably connected to the carriagealong a proximal side of the carriage; the frame extends from theproximal end of the implant to the distal end of the implant, and theactuator screw is connected to the frame and threadably connected to thecarriage along a distal side of the carriage; the frame is disposedwithin the proximal end of the implant; the frame extends from theproximal end of the implant towards the distal end of the implant; and,the implant further includes at least one post extending through theframe and into the carriage, slideably received in one of the frame orthe carriage, thereby configured to maintain an alignment of thecarriage along the longitudinal axis.

In yet further embodiments thereof, the implant further includes a firstpassage formed in a proximal end of at least one of the first and secondendplates, and a second passage formed in a proximal side of thecarriage, the first and second passages aligned to admit introduction ofa therapeutic matter into the open area of the carriage when the implantis implanted between bones of the joint; the frame connects to the firstand second endplates with a dovetail connection; the implant furtherincludes at least one radiopaque marker positioned in connection with atleast one of the first and second endplates, whereby an extent ofmovement of the connected endplate can be determined using imaging by arelative alignment of the radiopaque marker and a radiopaque element ofthe implant which does not move together with the connected endplate;ends of the at least one of the plurality of ramps of the carriage slidewithin grooves in at least one of the first and second endplates.

In another embodiment thereof, the frame includes an actuator screwbearing, a first tab extending away from the bearing in a firstdirection, and a second tab extending away from the bearing in adirection opposite to the upper tab, the first and second tabs formingedges; and the first and second endplates including grooves sized anddimensioned to slidingly receive the edges of the first and second tabs,respectively.

In accordance with another embodiment of the disclosure, an implant fortherapeutically separating bones of a joint, the implant defining alongitudinal axis extending between distal and proximal ends, theimplant comprises a first endplate configured to engage a first bone ofthe joint, and having an opening through the endplate transverse to thelongitudinal axis, and at least one ramped surface on a side opposite abone engaging side; a second endplate configured to engage a second boneof the joint, and having an opening through the endplate transverse tothe longitudinal axis, and at least one ramped surface on a sideopposite a bone engaging side;

a frame slideably connected to the first and second endplates to enablethe first and second endplates to move relative to each other at anangle substantially transverse to the longitudinal axis, in slidingconnection with the frame; an actuator screw rotatably connected to theframe; and a carriage (a) forming an open area aligned with the openingsin the first and second endplates and defining thereby a proximalcarriage side and a distal carriage side with respect to thelongitudinal axis, (b) threadably connected to the actuator screw,whereby rotation of the actuator screw moves the carriage with respectto the frame and the first and second endplates, the actuator screw notcrossing between the proximal carriage side and the distal carriageside; (c) including a plurality of ramps each mateable with at least oneof the at least one ramped surfaces of the first and second endplates,wherein when the carriage is moved by rotation of the actuator screw, atleast one of the at least one ramped surface of the first endplate andat least one of the at least one ramped surface of the second endplateeach slide along at least one of the plurality of ramps of the carriageto cause the endplates to move relative to each other in slidingconnection with the frame; and (d) at least one passage formed in aproximal side of the carriage in communication with at least oneproximal passage in at least one of the first or second endplates, thecommunicating passages configured to admit introduction of a therapeuticmatter into the open area of the carriage when the implant is implantedbetween bones of the joint.

In accordance with the disclosure, a method of therapeuticallyseparating bones of a joint, comprises inserting an implant defining alongitudinal axis extending between distal and proximal ends betweenbones of the joint, the implant including—a first endplate configured toengage a first bone of the joint, and having an opening through theendplate, and at least one ramped surface on a side opposite a boneengaging side; a second endplate configured to engage a second bone ofthe joint, and having an opening through the endplate, and at least oneramped surface on a side opposite a bone engaging side; a frameslideably connected to the first and second endplates to enable thefirst and second endplates to move relative to each other at an anglewith respect to the longitudinal axis, in sliding connection with theframe; an actuator screw rotatably connected to the frame; and acarriage (a) forming an open area aligned with the openings in the firstand second endplates and defining thereby a proximal carriage side and adistal carriage side with respect to the longitudinal axis, (b)threadably connected to the actuator screw, whereby rotation of theactuator screw moves the carriage with respect to the frame and thefirst and second endplates, the actuator screw not crossing between theproximal carriage side and the distal carriage side; and (c) including aplurality of ramps each mateable with at least one of the at least oneramped surfaces of the first and second endplates, wherein when thecarriage is moved by rotation of the actuator screw, at least one of theat least one ramped surface of the first endplate and at least one ofthe at least one ramped surface of the second endplate each slide alongat least one of the plurality of ramps of the carriage to cause theendplates to move relative to each other in sliding connection with theframe; and rotating the actuator screw after the implant is inserted tomove the first and second endplates relatively farther apart to separatebones of the joint.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings, in which:

FIG. 1 depicts an implant of the disclosure, together with three mountedbone screws;

FIG. 2 depicts the implant of FIG. 1, in a compressed or reduced heightconfiguration;

FIG. 3 depicts the implant of FIG. 1, in an expanded or increased heightconfiguration;

FIG. 4 depicts a carriage and frame of the implant of FIG. 1;

FIG. 5 depicts an endplate of the implant of FIG. 1;

FIG. 6A depicts a sagittal cross-section of the implant of FIG. 2;

FIG. 6B depicts a sagittal cross-section of the implant of FIG. 3;

FIG. 7A depicts an transverse cross-section of the implant of FIG. 2;

FIG. 7B depicts an transverse cross-section of the implant of FIG. 3;

FIG. 8 depicts an exploded view of the implant of FIG. 1;

FIG. 9 depicts a diagrammatic view of aspects of an implant inaccordance with the disclosure, in a reduced height configuration;

FIG. 10 depicts a the implant of FIG. 9, in an expanded heightconfiguration;

FIG. 11 depicts the implant of FIG. 1, implanted between adjacentvertebrae;

FIG. 12A depicts a front view of the implant of FIG. 1 having analternative blocking configuration, in a reduced height configuration;

FIG. 12B depicts the implant of FIG. 12A in an expanded heightconfiguration;

FIG. 13 depicts the implant of FIG. 12B, with bones screws inserted intothe implant;

FIG. 14 depicts inserting a trial of the disclosure, the trialrepresenting an implant of the disclosure, into the disc space, using atrialing tool of the disclosure;

FIG. 15 depicts an implantation and actuating tool of the disclosureinserting an implant of the disclosure into the disc space;

FIG. 16 depicts the implant and tool of FIG. 14, the tool havingexpanded the implant;

FIG. 17 depicts the implant and tool of FIG. 15, and a bone screw driverinserting a bone screw;

FIG. 18 depicts the implant of FIG. 13 secured between vertebrae;

FIG. 19 depicts an implant of the disclosure including a proximallydriven carriage;

FIG. 20 depicts the carriage of the implant of FIG. 19;

FIG. 21 depicts a lower endplate of the implant of FIG. 19;

FIG. 22 depicts an exploded view of the implant of FIG. 19;

FIG. 23 depicts a reduced height configuration of the implant of FIG.19;

FIG. 24 depicts an expanded height configuration of the implant of FIG.23;

FIG. 25 depicts a cross section of the implant of FIG. 23;

FIG. 26 depicts a cross section of the implant of FIG. 24;

FIG. 27 depicts the implant of FIG. 23, with bone screws inserted intothe implant;

FIG. 28 depicts the implant of FIG. 24, with bone screws inserted intothe implant;

FIG. 29 depicts a front view of the implant of FIG. 27;

FIG. 30 depicts a front view of the implant of FIG. 28;

FIG. 31 depicts a perspective view of the implant of FIG. 19, withoutbone screws inserted;

FIG. 32 depicts a front view of the implant of FIG. 30, without bonescrews inserted;

FIG. 33 depicts a side view of an alternative implant in accordance withthe disclosure, in a reduced height configuration;

FIG. 34 depicts the implant of FIG. 33, in an expanded heightconfiguration;

FIG. 35 depicts an exploded view of the implant of FIG. 33;

FIG. 36 depicts an enlarged cross section of a dovetail connection ofthe implant of FIG. 33;

FIG. 37 depicts a front view of the implant of FIG. 33, illustratingpassages for bone graft material;

FIG. 38 depicts a simulating of radiographic imaging of an implant ofthe disclosure, illustrating radiographic markers, the implant in areduced height configuration;

FIG. 39 depicts the implant of FIG. 38, the implant in an expandedheight configuration;

FIG. 40 depicts a bone funnel of the disclosure, used in connection withan implant of the disclosure;

FIG. 41 depicts an alternative implant of the disclosure, includinghinged endplates, in a reduced height configuration;

FIG. 42 depicts the implant of FIG. 41, in an expanded configuration;

FIG. 43 depicts the implant of FIG. 41, with a frame portion removed;

FIG. 44 depicts a cross section of an alternative implant of thedisclosure, in perspective, having an elongate actuator screw; and

FIG. 45 depicts the implant of FIG. 44, having a shortened actuatorscrew.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments are disclosed herein; however, it isto be understood that the disclosed embodiments are merely examples andthat the systems and methods described below can be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present subject matter in virtually anyappropriately detailed structure and function. Further, the terms andphrases used herein are not intended to be limiting, but rather, toprovide an understandable description of the concepts.

The terms “a” or “an”, as used herein, are defined as one or more thanone. The term plurality, as used herein, is defined as two or more thantwo. The term another, as used herein, is defined as at least a secondor more. The terms “including” and “having,” as used herein, are definedas comprising (i.e., open language).

Implants of the disclosure allow continuous expansion and retractionwithin a range of expansion. Lordosis of certain embodiments of implantsherein can be custom tailored to fit the anatomy of a specific patient.Additionally, implants of the disclosure enable distraction of vertebralbodies to a desired height, but can also be collapsed and repositioned,as therapeutically indicated for the patient.

With reference to FIGS. 1-3, implant or implant 100 is operative, whenpositioned between adjacent bones of a joint, such as for examplevertebrae 10, 12 (shown in FIG. 11), to stabilize a joint formed byadjacent vertebrae. Implant 100 has a collapsed state or height,illustrated in FIG. 2, and an expanded state or height, illustrated inFIG. 3. Implants 100 of the disclosure may be inset into theintervertebral disc space at a collapsed height, and then expand axially(superior/inferior) to restore height loss in the disc space. Theimplant provides distraction as well as achieves optimal heightrestoration. When inserted in a collapsed state, implants 100 reduceimpaction to tissue in the joint space during insertion, and form theleast visually blocking or obstructing profile.

Implant 100 includes two separable endplates 110, 112. A surface 114 ofan endplate 110, 112 can be provided with teeth or other projections 116which can penetrate body tissue to reduce a likelihood of migration ofimplant 100 after implantation. Implant 100 is further secured with oneor more bone screws 300, which pass through bone screw socket 118 withinimplant 100, and into body tissue of the patient. In the embodimentillustrated in FIGS. 1-3, three sockets 118 for three bone screws areprovided, the bone screws 300 further retained in connection withimplant 100 by blocking fasteners 120. Bone screw 300 can be a polyaxialscrew, and sockets 118 correspondingly shaped, whereby bone screw 300may be inserted into body tissue at an optimal angle with respect toimplant 100, whereby optimal purchase may be obtained, or certain bodytissue may be avoided.

Endplates 110, 112 are moveably connectable to an actuator 150 operableto change a relative relationship of endplates 110 and 112. Actuator 150includes a frame 152 rotatably supporting an actuator screw 154, and amoveable carriage 156. As actuator screw 154 rotates within frame 152,carriage 156 slides within frame 152, driven by cooperation betweenthreads 158 (FIG. 8) upon actuator screw 154, and mating threads 160within carriage 156. In the embodiment of FIGS. 1-3, endplates 110 and112 are formed in two connected portions, including a portion 122, 122Awhich can be polymeric, and a portion 124, 124A, which can be metallic.The portions are joined in the embodiment shown by screws 162, althoughother methods of combining the two connected portions 122, 124 or 122Aand 124A may be used, including a dovetail connection, or adhesive,possibly in combination with each other, or with endplate connectorscrews 162. Metallic portions 124, 124A can provide greater strength forportions of implant 100 which are under relatively greater stress, forexample portions through which a fastener may pass to anchor implant 100within the body. While portions 122, 122A, 124, 124A are described aspolymeric or metallic, it should be understood that other materials maybe used, and that the portions can be of dissimilar materials.

With reference to FIG. 2, it may be seen that implant 100 is in acompressed state, having a lower height relative to an expanded state,as shown in FIG. 3. A functioning of device 100 may be best understoodwith reference to FIGS. 9-10, which correlate with FIGS. 2-3,respectively, but which present a simplified view having certainelements eliminated or exaggerated, to ease understanding. Endplates 110and 112 are provided with ramped channels 164, 164A, and an open ramp166, 166A, sized to slidingly receive ramps 168, 168A and 170, 170Adisposed upon carriage 156. While two mating channels and ramps areillustrated for each endplate 110, 112, it should be understood thatone, or more than two, sets of channels and or ramps may be provided.Further, channels 164, 164A may alternatively be formed as ramps.However, a channel can operate to enable a reduction of height, havingan opposing ramp face, whereby rotation of actuator screw 154 in anopposite direction to expansion can drive endplates 110, 112 together,for example when pressure from body tissue is insufficient to collapseendplates 110, 112. Additionally, at least one channel can operate tofoster the maintenance of a connection between carriage 156 and anendplate 110, 112.

Carriage 156 is supported by frame 152 by lateral engagement means, inthis embodiment two support screws 174 engaged with carriage 156, andpassable through respective channels 176 formed in frame 152. Distal end172 of actuator screw 154 provides additional support for carriage 156.Actuator screw 154 is supported by a set screw 178, which passes throughand is rotatably supported within frame 152.

An actuator access port 180 permits passage of a tool, for example a hexdriver (not shown), into engagement with a proximal end 182 of actuatorscrew 154. As actuator screw 154 is turned, distal end 172 bears againsta thrust washer 184, and an end portion of frame 152. As actuator screw154, carriage 156 is driven along actuator screw by interaction ofthreads 158 and 160. As carriage 156 moves, endplates 110, 112 are urgedto move along ramps 168, 168A and 170, 170A, moving relatively apart,and increasing a height of implant 100. Endplates 110, 112 are preventedfrom moving together with carriage 156 by abutting against an endportion 186 of frame 152. In a given orientation, one of endplate 110and 112 is an upper endplate with respect to an orientation in astanding patient. However, implant 100 may, in some embodiments, beimplantable in either of opposite orientations, and thereforedesignations of upper and lower are provided for ease of understanding,only. It should be understood that only one of endplate 110, 112 may bemoveable with respect to the other. For example, in one embodiment,ramps 168A, 170A may not be provided, and endplate 112 may be attachedto frame 152.

FIG. 11 illustrates an implant 100 of the disclosure implanted betweenadjacent vertebrae 10, 12. Frame 152 defines a distal or leading end152A which is inserted first into the body, and a proximal or trailingend 152B which passes last into the body, the distal and proximal endsdefining a longitudinal axis extending therebetween. Implant 100 can beinserted into the body, and into a position between vertebrae, usingminimally invasive methods, for example using a small incision, andimplant 100 may be passed through a cannula or other structure whichmaintains a pathway through body tissue. Implant 100 may be insertedinto the spinal column through any approach, including anterior,anterolateral, lateral, or posterolateral. A portion of the discannulus, and nucleus pulposus may be removed in order to form a spaceinto which implant 100 may be inserted. When implant 100 is in acompressed, or reduced height configuration, dovetail guides 200, 202can be provided to foster maintenance of a relative orientation of upperand lower endplates during insertion or removal of device 100. Dovetailguides 200, 202 further stabilize endplates 110, 112 during expansion,and when implant 100 is expanded. Dovetail guides 200, 202, can have theform of a tongue and groove configuration, or other sliding matingconfiguration, with ends of ramps 168, 168A, for example.

Implant 100 can be inserted configured to have a lower height profile,as shown in FIG. 2, whereby an extent of distraction of body tissue maybe reduced during insertion. Moreover, to the extent that implant 100 isused to open a pathway towards an implantation site, trauma to adjacenttissue is reduced relative to inserting an implant having a final heightprofile. Once implant 100 is positioned between adjacent vertebrae,actuator screw is rotated by a tool. The tool may be positioned entirelywithin the body, or can extend from in interior of the body to outsidethe body, for example having a driving tip at one end and having ahandle at an opposite end, with a shaft extending into the body betweeneach end.

Once actuator screw 154 has been rotated to separate endplates 110, 112a desired amount, the tool is removed. At this point, actuator screw 154may be secured in place, for example using a mechanical block, or anadhesive, to prevent unintended rotation of actuator screw 154. Ascarriage 156 is slideably moved by rotation of actuator screw 154, aramp 166, 166A or a ramped surface of channel 164, 164A of at least oneof endplate 110, 112 slides against at least one ramp 168, 168A, 170, or170A of carriage 156, to cause the endplate to move along an axistransverse to the longitudinal axis of the frame, to increase a heightof the implant. Rotation of actuator screw 154 in an opposite directioncauses movement along an axis transverse to the longitudinal axis of theframe to decrease a height of the implant.

Polymeric insets, or a polymeric square nut, for example PEEK, can beprovided, engageable with threads 158 or other portion of actuator screw154, to provide additional friction to prevent height loss under load,particularly under cyclic loading. Similarly, once bone screws 300 havebeen inserted, blocking elements 120 may be rotated to extend over anend of bone screw head 302, preventing screw 300 from backing out. Asimilar mechanical block (not shown) may be provided for actuator screw154.

With reference to FIGS. 1-3, 5-8, it may be seen that a socket 118 for apolyaxial screw head 302 can be formed entirely within one of upper orlower endplate 110, 112, or may be formed partially within each ofendplate 110 and 112, whereby when implant 100 has been expanded to afinal height, the proportions of an interior of socket 118 are corrector substantially correct for retaining screw head 302. For example, inFIG. 8, metallic portion 124 forms an upper portion 190 of socket 118,and mating metallic portion 124A forms a lower portion 192 of socket118. In the embodiment illustrated in the figures, there are threesockets 118, and all are formed of upper and lower portions. However,there may be more or fewer sockets 118, and one or more sockets may beformed entirely in an upper or lower endplate.

In an embodiment, implant 100 of the disclosure provides an actuatorthat translates relative to the body by means of a threaded actuatorscrew 154. Ramps 168, 168A and 170, 170A on a carrier 152 mate withchannels 164, 164A, and or ramps 166, on endplates 110, 112. Lineartranslation of carriage 156 causes endplates 110, 112 to expand implant100 along an S/I axis with respect to the body. There can be dovetailguides that capture endplates 110, 112 when collapsing the implant.

Assembly screws 162 fasten endplates made of dissimilar materials, forexample PEEK polymeric portions 122, 122A to Titanium metallic portions124, 124A. A dovetail and press fit design can be used to connect thedissimilar endplate portions. A PEEK bushing or washer 184 is usedbetween the threaded actuator screw 154 and frame 152 to minimizefriction during expansion of implant 100. Support screws 174 andchannels 176 cooperate to form side or lateral stabilizers, and setscrew 178 supports a nose or leading end of carriage 156. Additionally,cooperating slots and projections (not shown) in carriage 156 and frame152 can be provided for further relative guidance and stability.

In one embodiment, three bone screws 300 are used to provide fixationinto adjacent vertebral bodies, two screws 300 passing through implant100 and into one vertebra, and one screw 300 passing through implant 100into another vertebra, although other combinations may be used. Bonescrews 300 can have spherical or otherwise curved heads, facilitatinginsertion at a desired angle, or may be provided to mate with socket 118in a fixed orientation, particularly depending on a diameter of a neckportion of screw 300. Cam style blocking fasteners 120 can be used toblock bone screws 300 from backing out after being inserted.

Implants of the disclosure enable a continuous expansion and retractionover a range of displacements according to predetermined dimensions of aspecific implant 100 design. This provides the ability to distractvertebral bodies to a desired height, but also to collapse the implant100 for repositioning, if therapeutically advantageous for the patient.Endplates 110, 112 may be shaped to form planes or surfaces whichconverge relative to each, to provide for lordosis, and can be providedwith openings, forming a graft chamber 204 through the openings andbetween the respective openings through which bone may grow, and intowhich bone graft material may be placed. Implant 100 may be used todistract, or force bones of a joint apart, or may be used to maintain aseparation of bones created by other means, for example a retractor.

Implant 100 may be fabricated using any biocompatible materials known toone skilled in the art, having sufficient strength, flexibility,resiliency, and durability for the patient, and for the term duringwhich the device is to be implanted. Examples include but are notlimited to metal, such as, for example titanium and chromium alloys;polymers, including for example, PEEK or high molecular weightpolyethylene (HMWPE); and ceramics. There are many other biocompatiblematerials which may be used, including other plastics and metals, aswell as fabrication using living or preserved tissue, includingautograft, allograft, and xenograft material.

Portions or all of the implant may be radiopaque or radiolucent, ormaterials having such properties may be added or incorporated into theimplant to improve imaging of the device during and after implantation.

For example, metallic portions 124, 124A of endplates 110, 112 may bemanufactured from Titanium, or a cobalt-chrome-molybdenum alloy,Co—Cr—Mo, for example as specified in ASTM F1537 (and ISO 5832-12). Thesmooth surfaces may be plasma sprayed with commercially pure titanium,as specified in ASTM F1580, F1978, F1147 and C-633 (and ISO 5832-2).Polymeric portions 122, 122A may be manufactured from ultra-highmolecular weight polyethylene, UHMWPE, for example as specified in ASTMF648 (and ISO 5834-2). In one embodiment, PEEK-OPTIMA (a trademark ofInvibio Ltd Corp, United Kingdom) may be used for one or more componentsof implant 100. For example, polymeric portions 122, 122A can be formedwith PEEK-OPTIMA, which is radiolucent, whereby bony ingrowth may beobserved. Other polymeric materials with suitable flexibility,durability, and biocompatibility may also be used.

In accordance with the invention, implants of various sizes may beprovided to best fit the anatomy of the patient. Components of matchingor divergent sizes may be assembled during the implantation procedure bya medical practitioner as best meets the therapeutic needs of thepatient, the assembly inserted within the body using an insertion tool.Implants of the invention may also be provided with an overall angulargeometry, for example an angular mating disposition of endplates 110,112, to provide for a natural lordosis, or a corrective lordosis, forexample of from 0° to 6° for a cervical application, although muchdifferent values may be advantageous for other joints. Lordotic anglesmay also be formed by shaping one or both of plates 110, 112 to haverelatively non-coplanar surfaces. Expanded implant heights, for use inthe cervical vertebrae for example, may typically range from 7 mm to 12mm, but may be larger or smaller, including as small as 5 mm, and aslarge as 16 mm, although the size is dependent on the patient, and thejoint into which an implant of the invention is to be implanted.Implants 100 may be implanted within any level of the spine, and mayalso be implanted in other joints of the body, including joints of thehand, wrist, elbow, shoulder, hip, knee, ankle, or foot.

In accordance with the invention, a single implant 100 may be used, toprovide stabilization for a weakened joint or joint portion.Alternatively, two, three, or more implants 100 may be used, at a singlejoint level, or in multiple joints. Moreover, implants 100 may becombined with other stabilizing means.

Additionally, implant 100 may be fabricated using material thatbiodegrades in the body during a therapeutically advantageous timeinterval, for example after sufficient bone ingrowth has taken place.Further, implant 100 is advantageously provided with smooth and orrounded exterior surfaces, which reduce a potential for deleteriousmechanical effects on neighboring tissues.

Any surface or component of the invention may be coated with orimpregnated with therapeutic agents, including bone growth, healing,antimicrobial, or drug materials, which may be released at a therapeuticrate, using methods known to those skilled in the art.

Devices of the disclosure provide for adjacent vertebrae to be supportedduring flexion/extension, lateral bending, and axial rotation. In oneembodiment, implant 100 is indicated for spinal arthroplasty in treatingskeletally mature patients with degenerative disc disease, primary orrecurrent disc herniation, spinal stenosis, or spondylosis in thelumbosacral spine (LI-SI). Degenerative disc disease is advantageouslydefined as discogenic back pain with degeneration of the disc confirmedby patient history and radiographic studies, with or without leg(radicular) pain. Patients are advantageously treated, for example, whomay have spondylolisthesis up to Grade 1 at the involved level. Thesurgery position implant 100 may be performed through an Anterior,Anterolateral, Posterolateral, and/or Lateral approach.

In a typical embodiment, implant 100 has a uncompressed height, beforeinsertion, of 12 to 18 mm, and may advantageously be provided incross-sections of 23×32 mm, 26×38 mm and 26×42 mm, with 4, 8, 12, or 16degree lordotic angles, although these are only representative sizes,and substantially smaller or larger sizes can be therapeuticallybeneficial. In one embodiment an implant 100 in accordance with theinstant disclosure is sized to be inserted using an MIS approach (areduced incision size, with fewer and shorter cuts through body tissue).

Implant 100 may advantageously be used in combination with other knownor hereinafter developed forms of stabilization or fixation, includingfor example rods and plates.

Referring now to FIGS. 13-18, implant 100 can be insert it into theintervertebral disc space at a collapsed height, and then expand it torestore the disc space height. Implant 100 provides distraction as wellas achieves optimal sagittal balance. As discussed, there are multiplemethods and approaches by which implant 100 can be inserted. FIGS. 14-18illustrate one possible method and approach of the disclosure. While aseries of numbered steps are described, it should be understood thatthere can be numerous other steps pertaining to the procedure, and thatthe steps described emphasize useful steps in the deployment of implant100 of the disclosure.

Step 1: Approach—An approach to the desired section of the spine isperformed using surgical instruments such as scalpels and retractors,for example using minimally invasive techniques.

Step 2: Preparation—Disc preparation instruments can be used to exposethe disc and remove disc material, for example using rongeurs and othersuitable instruments (not shown), to create a disc space 14.

Step 3: Trialing—As may be seen in FIG. 14, trialing for implantfootprint, height and wedge angle is performed to indicate which size ortype of implant 100 is to be used. An expandable trial, static trials,or a combination of each may be used. In FIG. 14, trial implant 320 istrial fit using trial insertion tool 400.

Step 4: Insertion—Graft material or other therapeutically beneficialmaterial is packed into graft chamber 204 of the selected implant 100when it is collapsed or partially expanded. As may be seen in FIG. 15,implant 100 is inserted into disc space 14 using insertion tool 410.Tool engagement formations 206 are provided on opposite sides of frame152 or one of endplate 124 or 124A, as can be seen in FIG. 1. Tool arms412 securely and releasably engage tool engagement formations 206, andalign an expansion driver 414 with actuator screw 154.

Step 5: Expansion—In FIG. 16, implant 100 is expanded, as describedherein, by turning actuator screw 154 using expansion driver 414. Afterexpansion, additional bone graft material can be packed through graftportals 208 into the central graft chamber 204 using a bone funnel 440(FIG. 40). A push rod (not shown) can be used for driving graft materialthrough funnel 440.

Step 6: Hole Preparation—Bone screw pilot holes can be formed into oneor more adjacent vertebrae, prepared using, for example, awls, drillsand or taps. Multiple pilot holes can be prepared first, or pilot holescan be prepared one at a time, before the insertion of each screw 300.During any of the steps herein, imaging can be carried out to avoiddamage to adjacent tissue.

Step 7: Screw Insertion—In FIG. 17, bone screws 300 are inserted usingbone screw driver 416. To facilitate access for bone screw driver 416,expansion driver 414 may be withdrawn from insertion tool 410. Afterbone screws 300 are inserted, they can be blocked from backing out usingblocking element 120. Lagging of the vertebral bodies can be performedbefore or after the bone screws are locked. Fluoroscopy or other imagingcan be used to confirm final placement. Imaging can also be used at anyof the steps to confirm work performed. Further, bone screw holepreparation and bone screw 300 insertion can be carried out prior toimplant 100 expansion, to promote anchoring of the implant duringexpansion. In FIG. 18, an expanded implant 100 can be seen betweenvertebrae, secured by bone screws 300. The foregoing method provides acustomized fit using implant 100, and minimizes disruption to patientanatomy.

Referring now to FIGS. 19-32, an alternative implant 100B of thedisclosure has a shorter actuator screw 154B relative to actuator screw154 of implant 100 of FIG. 1. Actuator screw 154B engages a proximal endof carriage 156B, and does not pass through graft portal 208B. A compactactuator frame 212 includes a screw bearing 210, and upper and lowertabs 214, 216, respectively. Endplate slots 218, 220 within endplates110B and 112B slidingly receive upper and lower tabs 214, 216. In thismanner, actuator screw 154B is rotatably fixed along a longitudinal axiswith respect to endplates 110B and 112B, the longitudinal axis indicatedin FIG. 19 to extend between distal (“D”) and proximal (“P”) ends.Endplates 110B, 112B can slide upon collar tabs 214, 216 to mutuallyseparate to form an expanded configuration of implant 100B. Actuatorscrew 154B can be rotatably retained within compact actuator frame 212,so that carriage 156B can be pushed or pulled in threaded engagementwith actuator screw 154B, without an axial displacement of actuatorscrew 154B. This can be accomplished, for example, by a clip or othercooperative engagement between compact actuator frame 212 or bearing210, and actuator screw 154B, or a blocking element (not shown)partially covering an end portion of actuator screw 154B. In anembodiment, tabs 214 and 216 form a dovetail connection with endplateslots 218, 220.

It should be understood that implant 100 may identified with a suffixherein, for example 100B, 100C, 100D, 100E, to indicate embodimentsillustrating various features of the disclosure. In consideration of theimpracticality of illustrating and describing every possible permutationof features, it should be understood that, where logical, features ofthe various implants may be substituted among the implants. Thus, all ofthe implants may collectively be referred to as implant 100, unless aspecific reference is made to a feature illustrated by a particularembodiment.

Actuator screw 1546B threadably engages carriage 156B at threads 160B,whereby rotation of screw 154B causes carriage 156B to move towards oraway from compact actuator frame 212. Carriage 156B has ramps 168, 168Aand 170, 170A, which engage corresponding endplate ramps 164, 164A, 166,166A as described with respect to implant 100. As actuator screw 154B isrotated, carriage 156 translates with respect to endplates 110B, 112B.As a result, carriage ramps 168, 168A and 170, 170A slide againstendplate ramps 164, 164A, 166, 166A, causing endplates 110B, 112B tomutually separate. In an embodiment, carriage 156B is polymeric atthreads 160B, and an interference fit is formed between actuator screw154B and threads 160B, whereby sufficient friction is created to resistunintended rotation of actuator screw 154B, with a consequential changein height of implant 100B.

Frame 152 slidingly bears against frame support edges 224 extendingalong endplates 110B, 112B, and is slidingly connected to carriage 156Bby carriage support screws 174. In this manner, carriage 156B islaterally supported, and inhibited from rotational movement, but maymove longitudinally along a path defined by carriage support channel 176and actuator screw 154B. Additionally, channels or dovetail guides 200,202 in endplates 110B, 112B receive mating end portions 200A, 202A ofcarriage ramps 168, 168A, 170, 170A, to further guide and stabilizeendplates 110B, 112B.

FIGS. 19-32 further illustrate an alternative blocking element 120B,which, as with other of the various alternative elements herein, may becombined with other implant embodiments herein. Element 120B forms ansliding block 226 within a block groove 228, block 226 and block groove228 forming a dovetail or other sliding mating engagement, wherein block226 is confined to movement along a path defined by block groove 228.Once bone screw head 302 is fully seated within bone screw socket 118,block 226 may be slid partially out of engagement with block groove 228to a position over bone screw head 302, thereby blocking a movement ofbone screw 300 out of engagement with body tissue. In the embodimentshown, two blocking elements 120B are illustrated, wherein a tool havingtwo end portions (not shown) can be inserted adjacent each block 226,and the tool rotated to move both blocks into a blocking position.Accordingly, blocks 226 together form substantially concentric arcspivoting about the same or close axes.

Implant 100B is configured to facilitate the insertion of graft materialor other therapeutic material through one or more of bone screw socket118 into graft chamber 204 formed by openings within endplates 110B,112B, and carriage 156B. After the material is inserted, bone screws 300may then be inserted into socket 118 and fastened to body tissue asotherwise shown and described herein. A bone funnel 440 (FIG. 40) may beused to urge material into graft chamber 204. Alternatively, onceimplant 100B is expanded, materials may be inserted into an endplate gap230 formed by a separation of endplates 110B, 112B, as may best be seenin FIGS. 30 and 32, which are cross-sections taken through compactactuator frame 212, and upper and lower tabs 214, 216.

It should be understood that endplates of the disclosure, in allembodiments, may be formed of a unitary material, as illustrated inFIGS. 19-32 for example, or multiple materials, as illustrated in FIGS.1-6 for example. Accordingly, endplates 110B, 112B may be formed ofmultiple materials, for example titanium for a proximal, bone screwengaging portion, and UHMWPE for a distal, bone engaging portion.Further, endplates 110B, 112B may be provided with teeth or otherprojections, to positively engage body tissue and reduce a likelihood ofundesired migration of implant 100B.

With reference to FIGS. 33-40, a spacer implant 100C includes frame 152Cwhich forms a dovetail engagement with upper and lower endplates 110C,112C. In this manner, endplates 110C, 112C are further stabilizedthroughout a range of expansion of implant 100C. As may be seen in FIG.36, a cross section of endplate portion 124C illustrates frame supportchannel 232 of endplate portion 124C is shaped to slidingly retain frameextension guide 234 of frame 152C (also visible in FIGS. 44-45). Itshould be understood that an inverse configuration can be created,wherein a channel is formed in frame 152C and an extension is formedfrom endplate portion 124C. Similar channels and extensions can beformed on opposing sides of frame 152C, as illustrated, with a framesupport channel 232 formed in lower endplate portion 124C′, as well. Inan embodiment, frame 152C can form an extended region 238 along all orpart of the dovetail engagement area of frame support channel 232 andextension guide 234. For example, frame 152C can extend in superior andinferior directions to extend from near an outer surface of endplate110C to near an outer surface of endplate 112C, or may extend over alesser distance. Channel 232 and extension guide 234 are illustrated astransverse to an A-P or longitudinal axis of implant 100C. In analternative embodiment, channel 232 and guide 234 are disposed at anon-transverse angle with respect to the longitudinal axis.

With reference to FIGS. 35 and 37, carriage 156C includes a graftchamber portal 236, providing access from a exterior to a proximal endof implant 100C into graft chamber 204, after implant 100C is implantedwithin the body. Carriage 156C includes two portals 236 specificallyformed to admit the passage of graft or other therapeutic materials,however one or more than two portals 236 can be provided. In theembodiment illustrated, graft chamber portals 236 are formed within aportion of carriage ramp 170, although other portions of carriage 156Cmay be shaped or opened in a like manner. A bone funnel 440 may be usedto direct material through one or more of graft chamber portal 236.

As can be seen in FIG. 35, actuator screw 154C includes actuator screwbearing 184C and lateral screw bearings 240, provided to promote smoothrotation of actuator screw 154C. Bearing channels 242 within actuatorscrew 154C can be provided to maintain an orientation of lateral screwbearings 240 within screw guide 246 of carriage 156C. In an embodiment,an interference fit is formed between lateral screw bearings 240 andscrew guide 246, to prevent unintended rotation of actuator screw 154C.To further stabilize carriage throughout at least a portion of its rangeof motion, stabilizing posts, screws, or pins 248 can be provided,connected to frame 152C, for example within frame pin bore 250 bythreads, adhesive, or an interference fit, and slideably engageablewithin pin bores 252 within carriage 156C. Alternatively, pins 248 canbe affixed to carriage 156C, and can slide within frame pin bores 152C.In an embodiment,

As can be seen in FIGS. 35 and 38-39, one or more radiographic markers254 are positioned within implant 100C, for example withinradiotransparent portions of implant 100C, or any other radiotransparentportion of the various embodiments herein. For example, a radiographicmarker can be positioned within polymeric endplate portion 122, 122A, sothat an expanded or contracted position thereof may be positivelyascertained using imaging. As may be seen in FIG. 39, radiographicmarkers 254A, 254B are oriented to be aligned with an end of carriageramps 168, 168A, which in this embodiment are radiopaque, only whenimplant 100C is fully expanded. To indicate an extent of expansion, oneor more radiopaque markers 254 can be positioned with respect to frame152, carriage 156, or any other portion of implant 100 which does notmove together with an endplate 110, 112, and which is radiopaque, orwhich is similarly configured with a radiopaque marker 254.

FIG. 40 illustrates a bone funnel 440 useable with implants 100, 100B,100C, 100D, 100E (collectively, herein, 100) of the invention. An outputaperture 442 is placed proximate an opening into an open area withinimplant 100, for example graft chamber 204. Bone graft material, and orother therapeutic agents, are collected within including for examplebone growth factors, antimicrobial agents, or other therapeutic isplaced into widened input chamber 444, and then pushed down pipe 446with a driver, for example a rod (not shown). A pipe connector 448 canbe provided, sized to correspond to graft chamber portal 236. Drivenbone graft material is passed into an interior of implant 100, where itmay have its intended therapeutic benefit upon contacting body tissue ofat least one vertebra.

In an embodiment, carriage ramps 168, 168A, 170, 170A can have differingramp angles and or sizes, wherein endplate ramps 166, 166A havecorresponding profiles and sizes. For example, if ramps 168, 168A areshorter than ramps 170, 170A, expansion will occur at a greater ratealong a proximal side of implant 100, and in this manner an angularorientation of the spine, for example lordosis, may be corrected.Similarly, ramps 170, 170A can be shorter than ramps 168, 168A.Alternatively, one side of ramp 168, 168A can be shorter than anotherside of ramp 168, 168A, with a corresponding difference along ramps 170,170A. In this manner, a sideways orientation of the spine, for exampleScoliosis, may be corrected.

FIGS. 41-43 illustrate an alternative implant 100D of the disclosure,which pivots proximate ends of endplates 110D, 112D, providing bothaxial translation, as indicated by arrows “A”, and pivoting, asindicated by arrows “B”. Axial translation is maintained using frame152C, together with frame extension guide 234 and frame support channel232, as described with respect to implant 100C. However, an endplatepivot 256 is formed between endplate portions 122D and 124D, and betweenendplate portions 122D′ and 124D′. FIG. 43 illustrates implant 100D withframe 152C removed, illustrating a endplate hinge 258 formed betweenendplate portions 122D and 122D′. Connected in this manner, endplateportions 122D and 122D′ pivot about endplate hinge 258, as well asendplate pivots 256. Accordingly, a height of implant 100D at a distalend of implant portions 122D and 122D′ is held constant, while aproximate end of implant portions 122D and 122D′ translates axially withendplate portions 124D and 124D′ to increase a height of implant 100D.

Implant 100D can be inserted into the intervertebral disc space at acollapsed height, and then expanded into lordosis to restore sagittalbalance and height loss in the disc space. Implant 100D providesdistraction as well as achieving optimal sagittal balance. Further,implant 100D reduces impaction to body tissue during insertion at acollapsed height, and gives a medical practitioner the capability tocontinuously adjust the lordotic angle of the supporting endplates tobest fit the patient's anatomy and therapeutic needs.

Endplate pivot 256 is formed as mating circular portions of endplateportions 122D and 124D, and of endplate portions 122D′ and 124D′. Whileone endplate portions forms an extension, and the other a receptacle, itshould be understood that this configuration may be reversed.

Endplate hinge 258 is formed as a flexible connector 260 extendingbetween endplate portions 122D and 122D′. In an embodiment, endplateportions 122D and 122D′ are molded as a single part from a polymeric orother flexible material, thus forming a living hinge. In a furtherembodiment, a hinge is formed between endplate portions 122D and 122D′by any known means, including a barrel or flag hinge, or a hinge similarin style to endplate pivots 256. In an alternative embodiment, endplatehinge 258 is formed in connection with frame 152C.

By providing both axial and pivoting movement of endplate portions,implant 100D enables the formation of an alternative supportingstructure, and in particular, a supporting structure with a convexconformity. This can be useful to correct particular spinal problems,including lordosis, for example.

With reference to FIGS. 44-45, which are cross-sections of analternative implant 100E of the disclosure, it may be seen that actuatorscrew 154E is rotatably connected to frame 152E, for example usingC-clip 262, as illustrated. An alternative method of rotatably securingactuator screw to frame 152E can include, for example, a leading setscrew 178 (see, e.g. FIGS. 6, 6A) that freely spins relative to frame152E, but is affixed to actuator screw 154E. An alternative methodincludes forming mating portions (not shown) upon frame 152E and screw154E.

Further stability can be provided for carriage 156C through the use ofstabilizing pins 248, frame pin bores 250, and pin bores in carriage152C, as described with respect to implant 100C herein.

In a further embodiment, actuator screw 154E′ is shorter than actuatorscrew 154E, and thereby reduces an obstruction of graft chamber 204. Atool can be passed through screw guide 246, and then through graftchamber 204, to engage actuator screw proximal end 182. Graft materialcan additionally be passed through screw guide 246, and placed withingraft chamber 204. Bone funnel 140 can be used to pass materials throughscrew guide 246, and pipe connector can be adapted or replaced to bestfit the dimensions of screw guide 246.

All references cited herein are expressly incorporated by reference intheir entirety. There are many different features to the presentinvention and it is contemplated that these features may be usedtogether or separately. Unless mention was made above to the contrary,it should be noted that all of the accompanying drawings are not toscale. Thus, the invention should not be limited to any particularcombination of features or to a particular application of the invention.Further, it should be understood that variations and modificationswithin the spirit and scope of the invention might occur to thoseskilled in the art to which the invention pertains. Accordingly, allexpedient modifications readily attainable by one versed in the art fromthe disclosure set forth herein that are within the scope and spirit ofthe present invention are to be included as further embodiments of thepresent invention.

What is claimed is:
 1. An implant for placement between bones, theimplant defining a longitudinal axis extending between distal andproximal ends, the implant comprising: a first end plate configured toengage a first bone, and having an opening through the endplate, and atleast one ramped surface on a side opposite a bone engaging side; asecond endplate configured to engage a second bone, and having anopening through the endplate, and at least one ramped surface on a sideopposite a bone engaging side; a frame at least partially surrounding atleast a portion of the first endplate; an actuator screw rotatablyconnected to the frame; and a carriage having an open area at leastpartially aligned with the openings in the first and second endplates,whereby rotation of the actuator screw moves the carriage with respectto the frame and the first and second endplates; and wherein thecarriage comprises a plurality of ramps each engageable with at leastone of the at least one ramped surfaces of the first and secondendplates, wherein when the carriage is moved by rotation of theactuator screw, at least one of the at least one ramped surface of thefirst endplate and at least one of the at least one ramped surface ofthe second endplate each move along at least one of the plurality oframps of the carriage to cause the endplates to move relative to eachother in connection with the frame, wherein the implant has a lengthextending from the distal end to the proximal end of the implant and awidth extending perpendicular to the length, the width of the implant isgreater than the length of the implant.
 2. The implant of claim 1, thefirst and second end plates move relative to each other only along anaxis substantially transverse to the longitudinal axis.
 3. The implantof claim 1, wherein at least one of the first and second endplatesincludes at least one aperture through which a fastener may pass tosecure the implant to one of the first or second bones.
 4. The implantof claim 1, further including a blocking mechanism configured to preventbacking out of a fastener passed through at least one of the first andsecond endplates and into one of the first or second bones.
 5. Theimplant of claim 4, the blocking mechanism including a blocking membermoveably retained within a channel between an unblocking position and ablocking position in which a portion of the blocking member overlaps aportion of the faster.
 6. The implant of claim 1, wherein the frame ismetallic.
 7. The implant of claim 1, further including a polymericmaterial configured to press against the actuator screw to reduce apotential for unintended rotation of the actuator screw.
 8. The implantof claim 1, wherein when the actuator screw is rotated in a firstdirection, a height of the implant transverse to the longitudinal axisis increased, and when the actuator screw is rotated in a seconddirection, a height of the implant transverse to the longitudinal axisis decreased.
 9. The implant of claim 1, wherein the actuator screw isthreadably connected to the carriage.
 10. The implant of claim 1,wherein the actuator screw is connected to the frame and threadablyconnected to the carriage.
 11. The implant of claim 1, wherein at leasta portion of the first endplate is polymeric and at least a portion ofthe second endplate is polymeric.
 12. The implant of claim 1, whereinthe frame extends from the distal end of the implant towards theproximal end of the implant.
 13. The implant of claim 1, furtherincluding at least one post extending through the frame and into thecarriage, received in one of the frame or the carriage, therebyconfigured to maintain an alignment of the carriage along thelongitudinal axis.
 14. The implant of claim 1, further including a firstpassage formed in at least one of the first and second end plates, and asecond passage formed in the carriage, the first and second passagesaligned to admit introduction of a therapeutic material into the openarea of the carriage when the implant is implanted between bones. 15.The implant of claim 1, wherein the frame connects to the first andsecond endplates with a dovetail connection.
 16. The implant of claim 1,wherein ends of the at least one of the plurality of ramps of thecarriage slide within grooves in at least one of the first and secondendplates.
 17. The implant of claim 1, wherein: the frame includes anactuator screw bearing, a first tab extending away from the bearing in afirst direction, and a second tab extending away from the bearing in adirection opposite to the upper tab, the first and second tabs formingedges; and the first and second endplates including grooves sized anddimensioned to slidingly receive the edges of the first and second tabs,respectively.
 18. An implant comprising: a first endplate configured toengage a first bone, and having an opening through the endplatetransverse to the longitudinal axis, and at least one ramped surface ona side opposite a bone engaging side; a second endplate configured toengage a second bone of the joint, and having an opening through theendplate transverse to the longitudinal axis, and at least one rampedsurface on a side opposite a bone engaging side; a carriage having anopen area aligned with the openings in the first and second endplates;and an actuator screw rotatably connected to the carriage, wherebyrotation of the actuator screw moves the carriage with respect to theframe and the first and second endplates; wherein the carriage comprisesa plurality of ramps engageable with at least one of the at least oneramped surfaces of the first and second end plates, wherein when thecarriage is moved by rotation of the actuator screw, at least one of theat least one ramped surface of the first endplate and at least one ofthe at least one ramped surface of the second end plate each translatealong at least one of the ramps of the carriage to cause the end platesto move relative to each other; and wherein the implant has a length anda width extending perpendicular to the length, the width of the implantis greater than the length of the implant.
 19. The implant of claim 18,at least one passage formed in the carriage in communication with atleast one passage in at least one of the first or second endplates, thecommunicating passages configured to admit introduction of a therapeuticmaterial into the open area of the carriage when the implant isimplanted between bones.
 20. The implant of claim 18, wherein the firstendplate includes a polymeric portion and a metallic portion and thesecond endplate includes a polymeric portion and a metallic portion.